We had a river probably 30 feet wide and 2 feet deep running into our pond from his field during that rain.
That's A LOT of inflow water for such a small BOW. I bet your pond water was flushed/turned several times. This has to have changed ALL the parameters in a short period...temperature and water chemistry flip flop. I have read that rainfall carries plenty of DO, but the rest of the parameters changed quickly stressing the fish and without aeration to keep the water column consistent with DO, even the available oxygen content changed.
Right, wrong, or indifferent: that's why I added aeration to my pond as it has excessive watershed. A massive inflow can be "settled down" some because all the water in the pond would have consistent properties and would not add to the "flip flop" with it's lower toxic waters. So far so good, but 30 feet wide and 2 feet deep sounds like a small river.
I'm rooting for you!
